Cyclic redundancy check (CRC) is a check method. In a communications system, cyclic redundancy check is a commonly used error check method. Specifically, a source end may calculate CRC of original data according to a generator polynomial. CRC may also be referred to cyclic redundancy check code (CRC). The source end adds the CRC after the original data, and sends, to a sink end, the original data to which the CRC is added. After receiving the original data to which the CRC is added, the sink end may check, according to the CRC and the generator polynomial, whether an error occurs in a process of transmitting the original data.
In the prior art, a CRC calculation circuit corresponding to a packet with a specific length is disposed in a receiver. After receiving the packet with a specific length, the receiver may check, according to the CRC calculation circuit, whether an error occurs in the packet with a specific length. The foregoing technical solution cannot be better applicable to a flexible Ethernet.